1. Field of the Invention
The present invention relates to apparatus and processes for the fabrication of microelectronic substrates. In particular, the present invention relates to a fabrication technology that encapsulates at least one microelectronic device within a microelectronic substrate core or that encapsulates at least one microelectronic device (without a microelectronic substrate core) to form a two-sided microelectronic substrate or a two layer microelectronic substrate.
2. State of the Art
Substrates which connect individual microelectronic devices exist in virtually all recently manufactured electronic equipment. These substrates are generally printed circuit boards. Printed circuit boards are basically dielectric substrates with metallic traces formed in or upon the dielectric substrate. One type of printed circuit board is a single-sided board. As shown in FIG. 23, single-sided board 300 consists of a dielectric substrate 302, such as an FR4 material, epoxy resins, polyimides, triazine resins, and the like, having conductive traces 304, such as copper, aluminum, and the like, on one side (i.e., first surface 306), wherein the conductive traces 304 electrically interconnect microelectronic devices 308 (shown as flip-chips) attached to the first surface 306. However, single-sided boards 300 result in relatively long conductive traces 304, which, in turn, result in slower speeds and performance. Single-sided boards 300 also require substantial surface area for the routing of the conductive traces 304 to interconnect the various microelectronic devices 308, which increases the size of the resulting assembly.
It is, of course, understood that the depiction of the dielectric substrate 302, the conductive traces 304, and the microelectronic devices 308 in FIG. 23 (and subsequently FIGS. 24 and 25) are merely for illustration purposes and certain dimensions are greatly exaggerated to show the concept, rather than accurate details thereof.
Double-sided boards 310 were developed to help alleviate the problem with relatively long conductive traces. As shown in FIG. 24, the double-sided board 310 comprises a dielectric substrate 302 having conductive traces 304 on the dielectric substrate first surface 306 and on a dielectric substrate second surface 312. At least one electrically conductive via 314 extends through the dielectric substrate 302 to connect at least one conductive trace 304 on the first surface 306 with at least one conductive trace 304 on the second surface 312. Thus, the microelectronic devices 308 on the dielectric substrate first surface 306 and on the dielectric substrate second surface 312 may be in electrical communication. The electrically conductive vias 314 are generally plated through-hole vias and may be formed in any manner known in the art.
FIG. 25 illustrates another board design, known as a multi-layer board 320. A multi-layer board 320 comprises two or more pieces of dielectric material (shown as first dielectric material 322 and second dielectric material 324) with conductive traces 304 thereon and therebetween with electrically conductive vias 314 formed through the first dielectric material 322 and the second dielectric material 324. This design allows for shorter traces and reduced surface area requirements for conductive trace 304 routing.
Although such boards have been adequate for past and current microelectronic device applications, the need for higher performance and shorter traces of substrate boards increases as the speed and performance of the microelectronic devices increase. Therefore, it would be advantageous to develop new substrates/boards, which achieve higher speed and performance.